Problem with "External Id" field when importing test cases to Jira using Zephyr Squad

I've given up on trying to make field 'Exernal ID" work, I've asked our IT to create a different short text field (Zephyr Squad ID) to contain the old test case identifier. I've mapped this field correctly when importing with Zephyr Squad and I can see its content in Jira's standard issue view. But it's still not visible in Zephyr Squad test cases view, this is clearly a Zephyr Squad Bug.